1. Field of the Invention
The present invention relates to a bottom valve apparatus of a hydraulic shock absorber.
2. Description of the Related Art
A bottom valve apparatus of a hydraulic shock absorber may be structured, as described in Japanese Utility Model Application Laid-open No. 3-22150 (patent publication 1), such that a push side flow passage 1A and a pull side flow passage 1B are formed in a bottom piece 1. A push side damping valve 2 opening and closing the push side flow passage 1A and a check valve 3 opening and closing the pull side flow passage 1B are respectively provided in a lower face side and an upper face side of the bottom piece 1, and a coil spring 4 urging the check valve 3 is fastened by a bolt 5 and a nut 6 which are provided in the bottom piece 1 (FIGS. 6A and 6B).
However, when the bottom valve apparatus is assembled, there is often a problem in that a leading end portion of the coil spring 4 is caught in the check valve 3. The bolt 5 in which the damping valve 2 is assembled is inserted from a lower surface side of the bottom piece 1, the check valve 3 and the coil spring 4 are arranged in the vicinity of a protruding end of the bolt 5 protruding to an upper face side of the bottom piece 1, and the nut 6 is screwed with the protruding end of the bolt 5. The check valve 3 and the coil spring 4 are centered by a centering guide 6A of the nut 6 so as to be fastened. However, in this case, there may be a situation that an end portion 4A of the coil spring 4 rotating together with a rotation of the nut 6 in a contacting side with the check valve 3 gets under the check valve 3 so as to be caught in a position between the bottom piece 1 and the check valve 3, during the centering of the check valve 3 (FIG. 6A).
As a result of a study carried out by the inventor of the present invention, it has been found that since a thread direction of the nut 6 (a rotating direction for moving the nut 6 in a fastening direction) is a right handed thread, and a winding direction of the coil spring 4 (a winding direction for moving the coil spring 4 in a direction apart from the nut 6) is also a right handed coil (FIG. 6B), the end portion 4A of the coil spring 4 in the contacting side with the check valve 3 moves in a direction which the check valve 3 is caught when the coil spring 4 rotates together with the rotation of the nut 6.